All of these problems are not because of the phone. When ur joystick moves by itself its most likely due to something force closing or moist screens with fingerprints on that area. Your char freezing up is probably due to ur screen being to moist again. I have all of these problems unfortunatly.

Tips on freezing character: Just wipe your screen every now and then to keep it dry. Also wipe your hands

Tips on moving joystick: when that happens, just turn your screen off and thwn turn it back on. That should fix the problem.